Record continuation turn-budget consumption decision

docs/roadmap/conversation-continuation.md

@@ -175,9 +175,9 @@ interpret the purpose of that work.
   questions without demonstrated shared answers across consumers. Applications
   can build those workflows from the selected branch-level capabilities.
 
-**Details to settle:** exact request/stop and outcome types, and turn-budget
-consumption belong to Decision 4. That decision records accepted response
-delivery, zero-turn budgets, cancellation, and minimal error/result semantics.
+**Implementation planning:** select exact request/stop and outcome types under
+Decision 4's accepted response delivery, turn-budget consumption, zero-turn
+behavior, cancellation, and minimal error/result semantics.
 Execution association and usage accounting belong to Decision 5. The sketches
 below illustrate the selected responsibility split; they do not settle the
 remaining public contracts.
@@ -274,8 +274,7 @@ bookkeeping. Callback model-call association remains part of Decision 5.
 
 ### 4. How Are Application Next Actions And Execution Outcomes Represented?
 
-**Status: response delivery, exhaustion, zero-turn budgets, cancellation, and
-minimal error/result semantics accepted; turn-budget consumption remains open.**
+**Status: accepted; exact public types remain for implementation planning.**
 The coordinator uses content-neutral next actions and distinguishes
 application-directed completion from exhaustion.
 
@@ -315,6 +314,25 @@ The alternative of treating zero as an immediate no-op with no callback is not
 selected: it would introduce special behavior and would not distinguish an
 already-complete interaction from one requesting more work.
 
+**Accepted turn-budget consumption:** at most N additional continuation
+executions may be started. The first operational error ends coordination.
+Starting a continuation consumes one turn even if preparation or generation
+subsequently fails. Callback invocations do not consume turns, and internal
+transport retries and structural repairs remain within the same turn. The
+starting exchange is outside the additional-turn budget. Requesting a turn
+when none remain produces exhaustion without starting an execution.
+
+For example, with a three-turn budget, a preparation failure in the second
+continuation returns that error and ends coordination. It does not start a
+third continuation or report exhaustion. The budget does not measure provider
+calls, work performed inside application callbacks, or cost.
+
+Counting only completed continuations was considered and not selected. Because
+operational errors already stop coordination, that alternative would primarily
+change bookkeeping. Use the straightforward executions-started interpretation
+without introducing public counters, budget refunds, or recovery machinery for
+this purpose.
+
 **Accepted cancellation behavior:** check the caller's context immediately
 before callback invocation, including the initial callback. If cancellation is
 already observed, do not invoke the callback; return the context error with its
@@ -382,12 +400,11 @@ use ordinary Go errors. A broader structured termination report was also
 considered and not selected: its additional metadata is unnecessary for the
 demonstrated minimal contract.
 
-**Details to settle:** what consumes an additional-turn budget when preparation
-or generation fails. Keep that budget distinct from structural repair and
-transport retry. Exact next-action, outcome, and optional-result types remain
-implementation planning details. Whether a completed run with failed structural
-validation produces a reusable exchange remains a Decision 1 question; the
-operational-error decision does not reclassify that validation result.
+**Implementation planning:** select exact types for next actions, outcomes, and
+the optional result under these accepted behaviors. Whether a completed run with
+failed structural validation produces a reusable exchange remains a Decision 1
+question; the operational-error decision does not reclassify that validation
+result.
 
 ### 5. How Are Related Executions And Usage Accounted For?